Fix action bar and buff bar spell tooltips showing 'Spell #xxx'

The action bar's inline Spell.dbc loader had a broken field index lookup:
operator[] on the layout map would silently insert 0 if 'Name' wasn't a
key, causing all names to be read from field 0 (the spell ID). Also the
once-only 'attempted' flag meant if assetMgr wasn't ready, it never retried.

Replace the duplicated broken DBC loading in the action bar and buff bar
with SpellbookScreen::lookupSpellName(), which reuses the spellbook's
already-correct loading (expansion layout + WotLK fallback). Remove the
now-unused actionSpellNames/actionSpellDbAttempted/actionSpellDbLoaded fields.

include/ui/spellbook_screen.hpp

@@ -35,6 +35,9 @@ public:
     void toggle() { open = !open; }
     void setOpen(bool o) { open = o; }
 
+    // Spell name lookup — triggers DBC load if needed, used by action bar tooltips
+    std::string lookupSpellName(uint32_t spellId, pipeline::AssetManager* assetManager);
+
     // Drag-and-drop state for action bar assignment
     bool isDraggingSpell() const { return draggingSpell_; }
     uint32_t getDragSpellId() const { return dragSpellId_; }